The objective of the proposed research is to obtain physiological and acoustical information on the process of learning compensatory speech patterns. Procedures involve altering the oral contours by wearing experimental alveolar-palatal prostheses, similar to orthodontic bite plates. Acoustical analysis of speech will be done, and physiological measurements made of jaw motions, larynx height, timing and location of tongue-palate contact, and breath pressure and flow. Subjects will be used who have normal speech as well as those who have presently normal sounding speech, but a history of sibilant articulation defects successfully remediated by speech therapy. Data will be recorded before and at the time of prosthesis insertion, after a period of adaptation lasting one or more weeks, and again after a month during which the prosthesis is not worn. A detailed descriptive study is planned on compensatory sibilant articulation. The relationship of pre-speech jaw activity to later jaw activity during speech utterance will be studied from the perspective of planning of speech motor sequences and compensatory strategies.